1. Field of the Invention
The present invention relates to a field emission display device and driving method, and more particularly, to a field emission display device and driving method for the same for displaying a uniform image on the apparatus by preventing voltage descending by a scan line or data line or compensating voltages applies to the respective lines, and its driving method.
2. Description of the Background Art
Recently, various flat panel display devices which can reduce weight and volume of a Cathode Ray Tube (hereinafter, as CRT) have been developed. The flat panel display device is divided to a Liquid Crystal Display (LCD), Field Emission Display (hereinafter, as FED), Plasma Display Panel, Electro-Luminescence and the like. To improve the displaying quality of the flat panel display device, researches for increasing luminescence, contrast and color purity are actively in progress.
Among them, the FED is divided into a tip type FED which emits electron using the tunnel effect by concentrating a high electric field in the acute emitter, and a flat FED which emits electron by concentrating a high electric field in a metal having a predetermined area.
The tip type FED emits electron at a conic protrusion portion which is manufactured with Si or Mo by applying an electric field at the electron emitting portion by applying a voltage to a gate electrode. Also, the flat panel FED forms a lamination structure including a metallic layer, insulation layer, semiconductor layer and the like and emits the electron outwardly form an electron emitting unit by injecting and passing electron from the metallic layer to the insulation layer.
In the tip type FED, discharging amount of electron is determined according to the characteristics of the emitter which is used for electron discharging. Therefore, every emitter must be manufactured uniformly, but with the present manufacturing process, it is difficult to manufacture an emitter uniformly and much time is taken to manufacture such emitter.
Also, in the tip type FED, since the electron is emitted from the acute emitter, a voltage of several tens to hundreds volts must be applied to cathode and gate electrodes, thus to consume much amount of power.
FIG. 1 is a drawing illustrating a cell of a field emission display (FED) in accordance with the conventional art. As shown in the drawing, each cell 100 of the flat panel FED includes an upper substrate 101 in which an anode electrode 102 and fluorescent material 103 are laminated, and a field emission array 105 which is formed on a lower substrate 104.
The field emission array 105 includes a scan electrode 108 formed on the lower substrate 104, an insulation layer 107 which is formed on the scan electrode 108 and a data electrode 106 which is formed on the insulation layer 107.
The scan electrode 108 supplies a current to the insulation layer 107, the insulation layer 107 insulates a portion between the scan electrode 108 and data electrode 106, and the data electrode 106 is used as a fetching electrode for emitting electron.
The FED in accordance with the conventional art will be described as follows.
To display an image on the display device, firstly, a scan pulse P of a negative polarity (−) is applied to the scan electrode 108 and a data pulse DP of a positive polarity (+) is applied to a data electrode 106. Then, the electrons are accelerated to the anode electrode 102 by tunneling the insulation layer 107 from the scan electrode 108 to the data electrode 106. The electrons excite the fluorescent material 103 by bumping into red, green and blue fluorescent materials 103. At this time, according to the fluorescent materials, a visible ray with a color among the red, green and blue colors is generated. Such flat panel FED can be driven with a lower voltage than that of the tip type FED, since the scan electrode 108 and data electrode 106 are installed having a predetermined area and facing each other.
Namely, voltages of only several volts to several tens of volts are applied to the scan electrode 108 and data electrode 106 of the flat panel FED and the scan electrode 108 and data electrode 106 for emitting electrons, have predetermined areas. Accordingly, the scan electrode 108 and data electrode 106 can be manufactured by a simpler manufacturing process than that of the tip type FED.
FIG. 2 is a block diagram showing a flat panel FED in accordance with the conventional art. As shown in the drawing, the flat panel FED includes a data driving unit 203 for driving the lines D1, D2, . . . , DM, a scan driving unit 201 for driving scan lines S1, S2, . . . , Sm, a first connector 202 which is installed in the lower substrate 205 and electrically connects the scan lines S1, S2, . . . , Sm and the scan driving unit 201, and a second connector 204 which is installed in the lower substrate 205 and electrically connects the data lines D1, D2, . . . , Dm and data driving unit 203.
The data driving unit 203 supplies a data pulse DP to the data lines D1, D2, . . . , Dm according to whether data are supplied and the scan driving unit 201 sequentially supplies a scan pulse SP to the scan lines S1, S2, . . . , Sm. Also, the first connector 202 is electrically connected with the scan driving unit 201 and supplies the driving signals applied from the scan driving unit 201 to the scan lines S1, S2, . . . , Sm. The second connector is electrically connected with the data driving unit 203 and supplies the driving signals applied from the data driving unit 203 to the data lines D1, D2, . . . , Dm.
FIG. 3 is a drawing illustrating a driving waveform which is supplied to the cell of the FED in accordance with the conventional art. As shown in the drawing, the scan pulse SP with negative polarity is sequentially supplied to the scan lines S1, S2, . . . , Sm of the conventional FED and data pulse DP with positive polarity which is synchronized to the scan pulse of negative polarity is supplied to the data lines D1, D2, . . . , Dm. In the cell to which the scan pulse SP and data pulse DP are supplied, electrons are emitted by voltage difference between the scan pulse SP and data pulse DP.
FIG. 4 is a drawing illustrating a cell arrangement of a general field emission display. As shown in the drawing, when the scan pulse SP of −5V is applied to the first scan line S1 and the data pulse DP of 5V is applied to the first data line D1, there occurs voltage difference of 10V in the first cell P1 which is formed in the first scan line S1.
On the other hand, since 5V, that is, only the data pulse is applied in the second to mth cells P2, . . . , Pm which are formed in the second to mth scan lines S2, . . . , Sm, the electrons are not emitted.
Then, the scan pulse SP and data pulse DP are sequentially applied to the mth scan line Sm by repeating such process and an image is displayed on the displaying device by driving the first to mth cells P1, P2, . . . , Pm. After displaying the image, the reset pulse RP with positive polarity is applied ot the first to mth scan lines S1, S2, . . . , Sm. Accordingly, electric charges which are charged in the first to mth cells P1, P2, . . . , Pm are removed.
However, the conventional FED has different voltage values of the scan pulses SP which are applied to the first position 401, second position 402, and third position 403. Namely, since the scan lines S1, S2, . . . , Sm of the FED have high resistance values, scan pulses SP with different voltage values according to the position of the scan lines S1, S2, . . . , Sm are applied by voltage descending caused by the high voltage values. For example, in case of the conventional FED of 5.3 inches, the respective scan lines S1, S2, . . . , Sm have resistance values between 100 to 150 Ω.
Therefore, in the FED in accordance with the conventional art, since different voltages are applied according to the position of the scan lines S1, S2, . . . , Sm, images with different luminances are displayed according to the position of the screen and accordingly, a uniform image could not be displayed on the FED.
Particularly, since such voltage descending phenomenon becomes more serious as the size of the FED increases, it could not manufactured with a large area.